The primary objective of this study is to examine the safety and immune responses elicited by combining MN rgp120 or bivalent AIDSVAX B/E vaccine with the adjuvant QS-21. The safety of the two expermental vaccines will be assessed when formulated with QS-21 or QS-21 plus alum. In particular, the study will address whether the new preparation of QS-21 in polysorbate 80 is less reactogenic than the QS-21 formulation used in AVEG Protocols.